diff options
Diffstat (limited to 'c/enc/hash_longest_match64_simd_inc.h')
-rw-r--r-- | c/enc/hash_longest_match64_simd_inc.h | 300 |
1 files changed, 300 insertions, 0 deletions
diff --git a/c/enc/hash_longest_match64_simd_inc.h b/c/enc/hash_longest_match64_simd_inc.h new file mode 100644 index 0000000..cd4e7b1 --- /dev/null +++ b/c/enc/hash_longest_match64_simd_inc.h @@ -0,0 +1,300 @@ +/* NOLINT(build/header_guard) */ +/* Copyright 2010 Google Inc. All Rights Reserved. + + Distributed under MIT license. + See file LICENSE for detail or copy at https://opensource.org/licenses/MIT +*/ + +/* template parameters: FN */ + +/* A (forgetful) hash table to the data seen by the compressor, to + help create backward references to previous data. + + This is a hash map of fixed size (bucket_size_) to a ring buffer of + fixed size (block_size_). The ring buffer contains the last block_size_ + index positions of the given hash key in the compressed data. */ + +#define HashLongestMatch HASHER() + +#define TAG_HASH_BITS 8 +#define TAG_HASH_MASK ((1 << TAG_HASH_BITS) - 1) + +static BROTLI_INLINE size_t FN(HashTypeLength)(void) { return 8; } +static BROTLI_INLINE size_t FN(StoreLookahead)(void) { return 8; } + +/* HashBytes is the function that chooses the bucket to place the address in. */ +static BROTLI_INLINE size_t FN(HashBytes)(const uint8_t* BROTLI_RESTRICT data, + uint64_t hash_mul) { + const uint64_t h = BROTLI_UNALIGNED_LOAD64LE(data) * hash_mul; + /* The higher bits contain more mixture from the multiplication, + so we take our results from there. */ + return (size_t)(h >> (64 - 15 - TAG_HASH_BITS)); +} + +typedef struct HashLongestMatch { + /* Number of hash buckets. */ + size_t bucket_size_; + /* Only block_size_ newest backward references are kept, + and the older are forgotten. */ + size_t block_size_; + /* Hash multiplier tuned to match length. */ + uint64_t hash_mul_; + /* Mask for accessing entries in a block (in a ring-buffer manner). */ + uint32_t block_mask_; + + int block_bits_; + int num_last_distances_to_check_; + + /* Shortcuts. */ + HasherCommon* common_; + + /* --- Dynamic size members --- */ + + /* Number of entries in a particular bucket. */ + uint16_t* num_; /* uint16_t[bucket_size]; */ + + uint8_t* tags_; + + /* Buckets containing block_size_ of backward references. */ + uint32_t* buckets_; /* uint32_t[bucket_size * block_size]; */ +} HashLongestMatch; + +static void FN(Initialize)( + HasherCommon* common, HashLongestMatch* BROTLI_RESTRICT self, + const BrotliEncoderParams* params) { + self->common_ = common; + + BROTLI_UNUSED(params); + self->hash_mul_ = kHashMul64 << (64 - 5 * 8); + BROTLI_DCHECK(common->params.bucket_bits == 15); + self->bucket_size_ = (size_t)1 << common->params.bucket_bits; + self->block_bits_ = common->params.block_bits; + self->block_size_ = (size_t)1 << common->params.block_bits; + self->block_mask_ = (uint32_t)(self->block_size_ - 1); + self->num_last_distances_to_check_ = + common->params.num_last_distances_to_check; + self->num_ = (uint16_t*)common->extra[0]; + self->tags_ = (uint8_t*)common->extra[1]; + self->buckets_ = (uint32_t*)common->extra[2]; +} + +static void FN(Prepare)( + HashLongestMatch* BROTLI_RESTRICT self, BROTLI_BOOL one_shot, + size_t input_size, const uint8_t* BROTLI_RESTRICT data) { + uint16_t* BROTLI_RESTRICT num = self->num_; + /* Partial preparation is 100 times slower (per socket). */ + size_t partial_prepare_threshold = self->bucket_size_ >> 6; + if (one_shot && input_size <= partial_prepare_threshold) { + size_t i; + for (i = 0; i < input_size; ++i) { + const size_t hash = FN(HashBytes)(&data[i], self->hash_mul_); + const size_t key = hash >> TAG_HASH_BITS; + num[key] = 65535; + } + } else { + /* Set all the bytes of num to 255, which makes each uint16_t 65535. */ + memset(num, 255, self->bucket_size_ * sizeof(num[0])); + } +} + +static BROTLI_INLINE void FN(HashMemAllocInBytes)( + const BrotliEncoderParams* params, BROTLI_BOOL one_shot, + size_t input_size, size_t* alloc_size) { + size_t bucket_size = (size_t)1 << params->hasher.bucket_bits; + size_t block_size = (size_t)1 << params->hasher.block_bits; + BROTLI_UNUSED(one_shot); + BROTLI_UNUSED(input_size); + alloc_size[0] = sizeof(uint16_t) * bucket_size; + alloc_size[1] = sizeof(uint8_t) * bucket_size * block_size; + alloc_size[2] = sizeof(uint32_t) * bucket_size * block_size; +} + +/* Look at 4 bytes at &data[ix & mask]. + Compute a hash from these, and store the value of ix at that position. */ +static BROTLI_INLINE void FN(Store)( + HashLongestMatch* BROTLI_RESTRICT self, const uint8_t* BROTLI_RESTRICT data, + const size_t mask, const size_t ix) { + uint16_t* BROTLI_RESTRICT num = self->num_; + uint8_t* BROTLI_RESTRICT tags = self->tags_; + uint32_t* BROTLI_RESTRICT buckets = self->buckets_; + const size_t hash = FN(HashBytes)(&data[ix & mask], self->hash_mul_); + const size_t key = hash >> TAG_HASH_BITS; + const uint8_t tag = hash & TAG_HASH_MASK; + const size_t minor_ix = num[key] & self->block_mask_; + const size_t offset = minor_ix + (key << self->block_bits_); + --num[key]; + buckets[offset] = (uint32_t)ix; + tags[offset] = tag; +} + +static BROTLI_INLINE void FN(StoreRange)(HashLongestMatch* BROTLI_RESTRICT self, + const uint8_t* BROTLI_RESTRICT data, const size_t mask, + const size_t ix_start, const size_t ix_end) { + size_t i; + for (i = ix_start; i < ix_end; ++i) { + FN(Store)(self, data, mask, i); + } +} + +static BROTLI_INLINE void FN(StitchToPreviousBlock)( + HashLongestMatch* BROTLI_RESTRICT self, + size_t num_bytes, size_t position, const uint8_t* ringbuffer, + size_t ringbuffer_mask) { + if (num_bytes >= FN(HashTypeLength)() - 1 && position >= 3) { + /* Prepare the hashes for three last bytes of the last write. + These could not be calculated before, since they require knowledge + of both the previous and the current block. */ + FN(Store)(self, ringbuffer, ringbuffer_mask, position - 3); + FN(Store)(self, ringbuffer, ringbuffer_mask, position - 2); + FN(Store)(self, ringbuffer, ringbuffer_mask, position - 1); + } +} + +static BROTLI_INLINE void FN(PrepareDistanceCache)( + HashLongestMatch* BROTLI_RESTRICT self, + int* BROTLI_RESTRICT distance_cache) { + PrepareDistanceCache(distance_cache, self->num_last_distances_to_check_); +} + +/* Find a longest backward match of &data[cur_ix] up to the length of + max_length and stores the position cur_ix in the hash table. + + REQUIRES: FN(PrepareDistanceCache) must be invoked for current distance cache + values; if this method is invoked repeatedly with the same distance + cache values, it is enough to invoke FN(PrepareDistanceCache) once. + + Does not look for matches longer than max_length. + Does not look for matches further away than max_backward. + Writes the best match into |out|. + |out|->score is updated only if a better match is found. */ +static BROTLI_INLINE void FN(FindLongestMatch)( + HashLongestMatch* BROTLI_RESTRICT self, + const BrotliEncoderDictionary* dictionary, + const uint8_t* BROTLI_RESTRICT data, const size_t ring_buffer_mask, + const int* BROTLI_RESTRICT distance_cache, const size_t cur_ix, + const size_t max_length, const size_t max_backward, + const size_t dictionary_distance, const size_t max_distance, + HasherSearchResult* BROTLI_RESTRICT out) { + uint16_t* BROTLI_RESTRICT num = self->num_; + uint32_t* BROTLI_RESTRICT buckets = self->buckets_; + uint8_t* BROTLI_RESTRICT tags = self->tags_; + const size_t cur_ix_masked = cur_ix & ring_buffer_mask; + /* Don't accept a short copy from far away. */ + score_t min_score = out->score; + score_t best_score = out->score; + size_t best_len = out->len; + size_t i; + /* Precalculate the hash key and prefetch the bucket. */ + const size_t hash = FN(HashBytes)(&data[cur_ix_masked], self->hash_mul_); + const size_t key = hash >> TAG_HASH_BITS; + uint32_t* BROTLI_RESTRICT bucket = &buckets[key << self->block_bits_]; + uint8_t* BROTLI_RESTRICT tag_bucket = &tags[key << self->block_bits_]; + PREFETCH_L1(bucket); + PREFETCH_L1(tag_bucket); + if (self->block_bits_ > 4) PREFETCH_L1(bucket + 16); + out->len = 0; + out->len_code_delta = 0; + + BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask); + + /* Try last distance first. */ + for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) { + const size_t backward = (size_t)distance_cache[i]; + size_t prev_ix = (size_t)(cur_ix - backward); + if (prev_ix >= cur_ix) { + continue; + } + if (BROTLI_PREDICT_FALSE(backward > max_backward)) { + continue; + } + prev_ix &= ring_buffer_mask; + + if (cur_ix_masked + best_len > ring_buffer_mask || + prev_ix + best_len > ring_buffer_mask || + data[cur_ix_masked + best_len] != data[prev_ix + best_len]) { + continue; + } + { + const size_t len = FindMatchLengthWithLimit(&data[prev_ix], + &data[cur_ix_masked], + max_length); + if (len >= 3 || (len == 2 && i < 2)) { + /* Comparing for >= 2 does not change the semantics, but just saves for + a few unnecessary binary logarithms in backward reference score, + since we are not interested in such short matches. */ + score_t score = BackwardReferenceScoreUsingLastDistance(len); + if (best_score < score) { + if (i != 0) score -= BackwardReferencePenaltyUsingLastDistance(i); + if (best_score < score) { + best_score = score; + best_len = len; + out->len = best_len; + out->distance = backward; + out->score = best_score; + } + } + } + } + } + /* we require matches of len >4, so increase best_len to 3, so we can compare + * 4 bytes all the time. */ + if (best_len < 3) { + best_len = 3; + } + { + const uint8_t tag = hash & TAG_HASH_MASK; + const uint32_t first4 = BrotliUnalignedRead32(data + cur_ix_masked); + const size_t max_length_m4 = max_length - 4; + const size_t head = (num[key] + 1) & self->block_mask_; + uint64_t matches = + GetMatchingTagMask(self->block_size_ / 16, tag, tag_bucket, head); + /* Mask off any matches from uninitialized tags. */ + uint16_t n = 65535 - num[key]; + uint64_t block_has_unused_slots = self->block_size_ > n; + uint64_t mask = (block_has_unused_slots << (n & (64 - 1))) - 1; + matches &= mask; + for (; matches > 0; matches &= (matches - 1)) { + const size_t rb_index = + (head + (size_t)BROTLI_TZCNT64(matches)) & self->block_mask_; + size_t prev_ix = bucket[rb_index]; + uint32_t current4; + const size_t backward = cur_ix - prev_ix; + if (BROTLI_PREDICT_FALSE(backward > max_backward)) { + break; + } + prev_ix &= ring_buffer_mask; + if (cur_ix_masked + best_len > ring_buffer_mask || + prev_ix + best_len > ring_buffer_mask || + /* compare 4 bytes ending at best_len + 1 */ + BrotliUnalignedRead32(&data[cur_ix_masked + best_len - 3]) != + BrotliUnalignedRead32(&data[prev_ix + best_len - 3])) { + continue; + } + current4 = BrotliUnalignedRead32(data + prev_ix); + if (first4 != current4) continue; + { + const size_t len = FindMatchLengthWithLimit(&data[prev_ix + 4], + &data[cur_ix_masked + 4], + max_length_m4) + 4; + const score_t score = BackwardReferenceScore(len, backward); + if (best_score < score) { + best_score = score; + best_len = len; + out->len = best_len; + out->distance = backward; + out->score = best_score; + } + } + } + bucket[num[key] & self->block_mask_] = (uint32_t)cur_ix; + tag_bucket[num[key] & self->block_mask_] = tag; + --num[key]; + } + if (min_score == out->score) { + SearchInStaticDictionary(dictionary, + self->common_, &data[cur_ix_masked], max_length, dictionary_distance, + max_distance, out, BROTLI_FALSE); + } +} + +#undef HashLongestMatch |